Thermal imaging cameras are used in a variety of situations. For example, thermal imaging cameras are often used during maintenance inspections to thermally inspect equipment. Example equipment may include rotating machinery, electrical panels, or rows of circuit breakers, among other types of equipment. Thermal inspections can use infrared (IR) energy detection to detect equipment hot spots such as overheating machinery or electrical components, helping to ensure timely repair or replacement of the overheating equipment before a more significant problem develops.
Depending on the configuration of the camera, the thermal imaging camera may also generate a visible light image of the same object. The camera may display the infrared image and the visible light image in a coordinated manner, for example, to help an operator interpret the thermal image generated by the thermal imaging camera. Unlike visible light images which generally provide good contrast between different objects, it is often difficult to recognize and distinguish different features in a thermal image as compared to the real-world scene. For this reason, an operator may rely on a visible light image to help interpret and focus the thermal image.
In applications where a thermal imaging camera is configured to generate both a thermal image and a visual light image, the camera may include two separate sets of optics: visible light optics that focus visible light on a visible light sensor for generating the visible light image, and infrared optics that focus infrared radiation on an infrared sensor for generating the infrared optics.
Cameras that comprise visible light optics and sensor as well as infrared optics and sensor may position these separate arrangements in separate locations on the camera. For example, the VL components may be located above, below, or to either side of the IR components. Accordingly, it is conceivable that, in some embodiments, the scene observed by the two sets of optics is substantially different, with one being offset from the other, that is, there may be a parallax offset incorporated between the images, which may be a manifestation of a registration error due to parallax from the two sets of optics.
In some previous embodiments, a user may adjust the focus of one or more sets of optics in an effort to resolve this parallax offset. Other cameras may be fixed-focus devices and may not have an adjustable focus with which to address the parallax offset. Some cameras can include distance-to-target measurements and adjust parallax based on such a measurement. However, in any case, situations may arise in which a focusing, distance-to-target, or factory calibrated parallax correction is insufficient and does not adequately correct for a parallax error. In addition, the incorporation of an add-on lens into a thermal imaging camera can act to compound or complicate a parallax correction.